For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve t...For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.展开更多
As the basis of designing and implementing a cyber-physical system (CPS), architecture research is very important but still at preliminary stage. Since CPS includes physical components, time and space constraints seri...As the basis of designing and implementing a cyber-physical system (CPS), architecture research is very important but still at preliminary stage. Since CPS includes physical components, time and space constraints seriously challenge architecture study. In this paper, a service-oriented architecture of CPS was presented. Further, a two-way time synchronization algorithm for CPS service composition was put forward. And a formal method, for judging if actual CPS service meets space constraints, was suggested, which was based on space-π-calculus proposed. Finally, a case study was performed and CPS business process designed by the model and the proposed methods could run well. The application of research conclusion implies that it has rationality and feasibility.展开更多
An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on...An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.展开更多
基金Supported by the Ministerial Level Foundation(2102812)
文摘For the high precision time synchronization demand of ships, advantages and disadvantages of the present time transfer methods are analyzed, the two-way microwave time transfer （TWMTT） method is adopted to resolve the time synchronization problem in the Naval Ship Formation. After expounding the principle and system composition of TWMTT method, the various factors influencing the synchronous precision are analyzed, such as time-interval measurement error, TWMTT equipment delay error, signal propagation error in air, and signal delay error caused by shipping. To improve the time synchronization precision, all the error sources above are deduced with mathematical measures to definite the critical one, and the signal processing measures such as Pseudo code spread spectrum time comparison signal generation technology, FFT fast acquisition technology and precise tracking technology are used into the modem which is the core equipment of the TWMTT. And, calibration method of TWMTT equipment delay are developed. Through theoretical a- nalysis and simulation verification, the precision of shipboard two-way microwave time synchroniza- tion can reach 1 ns.
基金National High-Tech Research and Development Programs of China( 863 Program) ( No. 2011AA010101,No. 2012AA062203) National Natural Science Foundation of China ( No. 61103069 ) Key Research Project of Shanghai Science and Technology Committee,China( No. 10dz1122600)
文摘As the basis of designing and implementing a cyber-physical system (CPS), architecture research is very important but still at preliminary stage. Since CPS includes physical components, time and space constraints seriously challenge architecture study. In this paper, a service-oriented architecture of CPS was presented. Further, a two-way time synchronization algorithm for CPS service composition was put forward. And a formal method, for judging if actual CPS service meets space constraints, was suggested, which was based on space-π-calculus proposed. Finally, a case study was performed and CPS business process designed by the model and the proposed methods could run well. The application of research conclusion implies that it has rationality and feasibility.
基金Supported by the National High Technology Research and Development Program of China(2012AA1406)
文摘An improved measurement algorithm, based upon the theory of two-way time transfer （ TWTT）, is proposed to measure satellites with high speeds. The algorithm makes theoretical analyses and corresponding deductions on a relative motion model of two satellites, and eliminates the measurement error caused by the equipment delay when a satellite moves at a high speed. Theoretical analysis and simulation results demonstrate that in comparison with the conventional TWTT algorithm, the proposed algorithm can significantly enhance the measurement accuracy of the inter-satellite ranging and time synchronization, and the algorithm is more effective with the relative velocity between the satellites and transmitting delay becoming larger.
